1. Field of the Invention
This patent application relates to a teat cup liner for vacuum operated automatic milking machines.
2. Background
Conventional automatic milking machines utilize teat cup assemblies for milking mammals, such as cows. The teat cup assembly has a hollow, rigid outer shell or cup adapted to be attached to a pulsating vacuum line, and a resilient, tubular liner or inflation installed within the shell in a manner to form a seal at both ends of the shell and define a chamber between the shell and the inflation.
The typical inflation includes an upper portion having a teat receiving mouth, a vacuum chamber and upper vacuum channel or barrel which is housed in the shell, and a lower short milk tube section which extends downwardly out of the shell and is attached to a milk claw for collecting milk. An animal's teat is inserted into the receiving mouth and extends into the vacuum chamber and barrel. The mouth, vacuum chamber and barrel are each sealingly engaged with the upper and lower ends of the shell to form an annular chamber surrounding the barrel between the shell and the barrel. The shell is attached to a pulsating vacuum line causing the pressure in the annular chamber to alternate between sub-atmospheric and atmospheric pressure. A vacuum maintained in the milking claw causes a constant vacuum to be applied to the inside of the liner. The vacuum draws the milk from the teat through the short milk tube while the alternating pressure in the annular chamber creates a teat massaging action as the vacuum chamber and barrel collapses onto the teat stopping milk flow when fully collapsed and initiating milk flow when open.
Typically milking teat liners are composed of elastomeric materials, such as natural or synthetic rubber or silicone rubber, due to the resilient nature of such materials. For instance, rubber liners are capable of recovering their original size and shape after repeated deformation. Natural or synthetic rubber compositions are more resistant to tearing or ripping, but are subject to attack by oils, butterfats, teat treatment preparations and other chemicals used in the milking process. On the other hand, silicone rubbers are substantially less vulnerable to attack by such chemicals leading to a relatively longer useful life, but silicone rubber tends to tear and puncture more easily than natural or synthetic rubber.
U.S. Pat. No. 6,164,243 to Larson describes a milking inflation which has a generally triangular suction sleeve. Each side of the generally triangular suction sleeve has a convex cross-section. The convex cross-section allows the sleeve to collapse on the teat at a more consistent time-frame as opposed to a straight-side triangular shape where the center of each face would contact the teat before the vertices. Although the convex cross-section improves performance, the tight vertices of the triangle resist collapse thereby limiting the sleeve contact with the teat. This lack of contact reduces milking efficiency.
U.S. Pat. No. 7,578,260 to Shin provides a milking liner having a short milk tube with external ribs running the length of the milk tube to prevent the tube from collapsing under vacuum and to prevent kinking of the milk tube during use and storage. Additional longitudinal ribs run a shortened length of the milk tube proximate the end of the milk tube which connects to the milking claw. The additional ribs further prevent the milk tube from bending and kinking when the milking inflation is connected to the milking claw. While aiding in preventing unwanted kinking of the milk tube, the ribs suffer some significant drawbacks. The plurality of ribs creates an overly rigid milk tube end. This rigidity minimizes the flexibility of the milking tube and prevents necessary flexing of the milk tube when the milking inflation is inserted on an animal's teat. If the animal moves or shifts position, the milking inflation may slip off of the teat preventing milking of the animal. Further, the milk tube's rigidity also increases the possibility that the milk tube will become dislodged from the milking claw during use. Thus, milk extracted from the animal may not be captured by the milking system.
U.S. Pat. No. 6,745,718 to Chowdhury describes a teat liner having a figured mouthpiece to reduce slipping of the liner off of the teat during use. The inner wall of the mouthpiece barrel is provided with an embossed pattern which is used to grip the teat. Numerous possible embossed textures are disclosed. However, embossing the inner wall may aid in preventing a teat from slipping out of the liner, but the textured inner surface may promote damage to the teat and bacteria growth.
U.S. Pat. No. 5,572,947 to Larson calls for two grooves on a short milk tube with a first, upper groove used to promote bending of the tube into a generally 90 degree position while a bottom groove promotes shut off of milk flow. While the grooves allow the short milk tube to be bent and positioned at an extreme angle the '947 patented liner has potential drawbacks. First, the grooves circumscribe the entire tube and structurally form a wall that is thinner in diameter than in the region of the grooves. This thin wall can crack and/or tear, particularly after frequent flexing and pinching of the short milk tube at these locations. Secondly, the grooves described in the '947 patent dictate the position of the milk claw relative to the milking inflation so that the flexing of the short milk tube is controlled and is limited to one optimal location and degree of bending. This “one optimal” position is impractical as the mammal (i.e. cow) can shift position during milking and the position increases the time required to prepare the animals for milking and decreases milking employee efficiency.
Thus, there is clearly an unmet and long-felt need for a low-slip high-capacity teat liner which also has a kink-resistant milk tube without the necessity of a high vacuum level.